I have a Snap-on tool box designed for the backs of vans. Like your boxes my last failed at the welds. The weight of tools and the flexing of box, van etc saw these welds fail and the box scrap.

My Snap-on is about 25years old and still as good as the day it was bought. It has the old slider rails for the drawers, so i disagree saying ball bearings are the only way. Good products designed for the job is the best way.

You get what you pay for. my previous boxes cost £100 and lasted 5 years. My £500 snap-on still going strong 25 years later. So only now is it saving me money LOL

For going on site I have an old BOSS warehouse tool box. like a doctors case, ideal and still going strong 15 years after leaving BOSS. I also have a plastic stanley box with wheels to drag in the heavy stuff. I got it from B&Q, Must say I like the plastic it can be stood on and always looks tidy. No paint or rust years later